The influence of sleeping position on functional residual capacity and effective pulmonary blood flow in healthy neonates

Abstract

Variation in body position has been shown to affect respiratory function in adults and neonates with and without respiratory illness. At present it remains unclear why respiratory function should be affected by different body positions. We hypothesized that the effect of body weight on the relatively compliant chest wall of the newborn infant in the prone position would cause a reduction in functional residual capacity (FRC) and a compensatory improvement in ventilation/perfusion matching as measured by effective pulmonary blood flow. To evaluate this, a paired crossover study was performed on 12 normal newborn infants. The inert gas (argon) rebreathing method adapted for neonates was used to measure FRC. Simultaneously effective pulmonary blood flow (QPeff) was determined using Freon 22 and a mass spectrometer with computerized analysis. The babies were studied in three different positions in random order: prone, supine, and right lateral decubitus. The means (95% confidence intervals) of the three groups for FRC were 23.8 (19.2 to 28.4), 23.8 (20.2 to 27.5), and 24.3 (19.5 to 29.2) ml/kg, respectively (P = 0.59), and for QPeff were 104 (91 to 116), 108 (95 to 122), 109 (97 to 122) ml/kg‐min, respectively (P = 0.11). Thus no significant differences were demonstrated. In nine of the babies, a repeat supine measurement was taken at the end of the study to assess repeatability of the method. In these nine babies alone the results were 22.7 (19.1 to 26.3) and 22.1 (18.6 to 25.6) ml/kg for FRC, and 102 (89 to 116) and 98 (90 to 107) ml/kg‐min for QPeff. The coefficients of repeatability were 4.7 ml/kg for FRC (21%) and 30 ml/kg‐min for QPeff (30%). Pediatr Pulmonol. 1996; 22:342–347. © 1996 Wiley‐Liss, Inc.

Sleeping position, oxygenation and lung function in prematurely born infants studied post term

“…In contrast, in healthy term born neonates studied in the first 72 h after birth, lung volumes were similar in the prone and supine positions,7 and, among infants studied at a median age of 2.4 months, no significant effect of positioning on oxygenation saturation was noted 8. The latter study population, however, included infants born at term as well as those born prematurely, and, although the infants were all at increased risk of SIDS (previously experienced an acute life-threatening event, inability to fall asleep in their normal position, very premature birth, upper airway obstruction, or had a sibling who had died from SIDS), none had respiratory distress 8.…”

“…None of the infants currently studied were oxygen-dependent when examined post term, but all had had respiratory distress syndrome and half the population had had BPD. Thus, a possible explanation for the differences in position-related effects on oxygen saturation between studies7 – 9 is the presence or absence of previous or current lung disease. The impact of positioning on both lung volume and oxygenation has rarely been examined.…”

Effect of Prone and Supine Positions on Functional Residual Capacity, Oxygenation, and Respiratory Mechanics in Ventilated Infants and Children

“…FRC is known to increase in spontaneously breathing adult subjects in the prone position, in both awake (19) and anesthetized (18) states, and there are sound theoretical reasons why this should occur (1). To the best of our knowledge, changes in FRC with position have not been reported previously in critically ill children, although a study in spontaneously breathing intubated neonates with mild lung disease failed to demonstrate any increase in FRC despite significant increases in oxygenation (6) and a study in healthy neonates similarly reported no changes in FRC in prone versus supine positions (20). The combination of neuromuscular blockade and positive pressure ventilation may be expected to attenuate position-related changes in lung volumes and mechanics compared with those seen in spontaneously breathing subjects.…”

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants

“…Others, however, have suggested that lung volume may be lower in the prone position because of the compressing effect of the infant's body weight on the relatively compliant chest wall. 26 The impact of posture on functional residual capacity of preterm infants at a postconceptional age of near term is unexamined but, in healthy full term infants, no posture related significant changes in either functional residual capacity or effective pulmonary blood flow were shown in the first days after birth. 26 Prone posture also influences the likelihood of gastrooesophageal reflux.…”